1. Field of the Invention
The present invention is related with a vehicle navigation system which can search for generating multiple routes from an original position to a destination.
2. Description of the Related Art
A conventional vehicle navigation system generates multiple routes from an original position, such as a present position, to a destination when the, destination is determined, and the multiple routes are displayed on a map in the display device. Also, the conventional vehicle navigation system allows the user to select a preferred route among the multiple routes as a guidance route (see JP-A-2002-202137). In the above system, a guidance route is selected based on a condition, such as a street name, the fee of toll road or turnpike toll, a required time. For example, in a case, where the street name is used for the selection, when a street name key is operated, the names of highways will be displayed in a list on a display device. When the user selects a preferred street name in the list, the route including the road of the selected name is highlighted. When a determination key is operated in the above situation, the highlighted route is confirmed as final and determined as the guidance route.
Another conventional system search for a route associated with a shortest distance and a route associated with a shortest required time from the present position to the destination when the destination is set up, and both the routes are displayed on the display device. When the user selects one of the routes, which are displayed, the system confirmed the selected route as the guidance route (refer to JP-A-H1-130299).
Further, another conventional vehicle navigation system generates multiple routes with a rank order in consideration of minimizing the cost of the line segments from the original position to the destination. The system displays the multiple routes on the map in display device to facilitate the visual recognition and allows the user to select a preferred route (JP-A-H5-164566).
In each system described in JP-A-2002-202137, JP-A-H1-130299, and JP-A-H5-164566, the generated or calculated multiple routes are simultaneously displayed in the display device. However, because each route usually includes curves that bend vertically and horizontally in the display, it is difficult to compare lengths of distance of the multiple routes based on the appearance of the routes. For the above reason, when selecting one route among the multiple routes, the lengths of the distances cannot be easily compared with each other even when the distance is necessary as a criteria for the selection.
In the vehicle navigation system of JP-A-2002-202137, when the required time is used for the selection, the route having the shortest required time among multiple searched routes or calculated routes displayed on the display device is highlighted. For example, the route to take less than 20 minutes, the route to take less than 25 minutes, the route to take less than 30 minutes, the route to take less than 35 minutes, and the route to take less than 40 minutes are displayed in a list. However, for example, when there are two routes, both of which take more than 20 minutes but equal to or less than 25 minutes, the route taking the shorter required time than the other cannot be distinguished from the other.